Traditional diffusion NMR techniques suffer from several drawbacks that limit their applications. Overlapping peaks from different molecules can make it impossible to determine diffusion coefficients in complex mixtures. Particles that diffuse too slowly, such as large proteins and synthetic polymers, also pose difficulties for diffusion measurements, as the distance they diffuse over during the experimental duration is too small to result in an appreciable change, which needs high gradient strength to make an efficient decay for accurate diffusion measurement. However the hardware of current NMR spectrometers is limited on the gradient power for this application. It was therefore clear that a new technique was necessary that would be able to improve the resolution and reduce the complexity of the system. This has been accomplished in this research by incorporating Hadamard transfer into a diffusion NMR experiment that can generate two-dimensional spectra in a short amount of time and contains only explicitly selected resonances while also implementing multiple-quantum coherence filtration to enhance the response efficiency of signal decay to the gradient. The multiple-quantum selection creates spectra containing only signals of specific multiplicity like CH, CH2 or CH3 for 1H-13C correlations thus further enhance the resolution for the diffusion measurements. These two techniques have, until now, not been combined into a single diffusion NMR experiment, which will generate high resolution pseudo 2D NMR data that are diffusion attenuated by applied gradient power at the maximum attainable quantum coherence level of the system.

Novel diffusion NMR experiment for effective study of macromolecules

252nd National Meeting (2016)

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